Pollux,Capella Binary Stars,Albireo Binary Stars and Arcturus
Pollux (β Gem, β Geminorum, Beta Geminorum) is a star in the northernconstellation of Gemini, the Twins. With an apparent visual magnitude of 1.1,[2] Pollux is the brightest star in the constellation; brighter even than its neighbor Castor (Alpha Geminorum). Parallax measurements from theHipparcos astrometry satellite[13][14] place it at a distance of about 33.78light-years (10.36 parsecs) from Earth[1]. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.[15] In 2006, Pollux was confirmed to have an extrasolar planetorbiting it.[7] Capella (α Aurigae, α Aur, Alpha Aurigae, Alpha Aur) is the brightest star in the constellation Auriga, the sixth brightest star in the night sky and the third brightest star in the northern celestial hemisphere, after Arcturus and Vega. Although it appears to be a single star to the naked eye, it is actually a star system of four stars in two binary pairs. The first pair consists of two bright, large type-G giant stars, both with a radius around 10 times the Sun's, in close orbit around each other. These two stars are thought to be cooling and expanding on their way to becoming red giants. The second pair, around 10,000 astronomical unitsfrom the first, consists of two faint, small and relatively coolred dwarfs.[11][12] The Capella system is relatively close, at only 42.2 light-years (12.9 pc) from Earth. Albireo (β Cyg, β Cygni, Beta Cyg, Beta Cygni) is the fifth brightest star in the constellation Cygnus. Although it has the Bayer designation beta, it is fainter than Gamma Cygni,Delta Cygni, and Epsilon Cygni. Albireo appears to the naked eye to be a single star of magnitude 3 but through a telescope, even low magnification views resolve it into adouble star. The brighter yellow star (actually itself a very close binary system) makes a striking colour contrast with its fainter blue companion star.[6] Arcturus ( /ɑrkˈtjʊərəs/; αBoo, αBoötis, Alpha Boötis) is the brightest star in the constellation Boötes. To the naked eye, orange-yellow Arcturus has a visual magnitude of −0.04, making it the brightest star north of the celestial equator, and the fourth brightest star in the night sky, after −1.46 magnitude Sirius, −0.86 magnitude Canopus, and −0.27 magnitude Alpha Centauri. However, Alpha Centauri is a bright binary star, whose unresolved components to the naked eye are both fainter than Arcturus. This makes Arcturus the third brightest ''individual''star, just ahead of Alpha Centauri A (αCen A), whose visual magnitude is −0.01. Arcturus is visible from both hemispheres in the sky, as it is located less than 20 degrees north of the celestial equator. The star culminates at midnight on about the 30th April, being visible during the northern spring or the southern autumn. From the northern hemisphere, an easy way to find Arcturus is to follow the arc of the handle of the Big Dipper. By continuing in this path, one can find Spica, "Arc to Arcturus, then spike to Spica." The star is also a member of the Local Interstellar Cloud.